Stage One: pre-Industrial Revolution, birth rates and death rates are both high, the level of the population stays the same
Stage Two: in a developing country death rates tents to diminish while birth rates stay high: population is growing
Stage Three: thanks to the better economic and living conditions, births starts to decrease
Stage Four: birth rates and death rates are both low, so population is stabilizing. Most of today's developed countries are in this stage
Stage Five (possible stage): here the birth rates have fallen below death rates, so the quantity of older people is bigger than the quantity of younger ones